Yes, I know what you mean: they did the same to us about 2 years ago in the Aurora, CO store. It was the assistant manager- he told us we would get 10% off the first purchase and then 5% from thereafter. We read the "small print" and challanged him to his lie.
In fact, there is a complicated tier of spending amounts and we found you have to spent something like 20K a month to get the 5%. (don't hold me to that figure- it's been a few years.) Besides, we wouldn't use Discover if they gave us 75% off!. They have the worst customer service in the world.) So, in closing I can tell you that you probably were not lied to, but rather I will suggest to you that most of the management and staff at Sam's are ill-trained in those areas of knowledge.